Corrugated cardboard is commonly used in the manufacture of shipping cartons having a wide variety of uses. The manufacturing of corrugated cardboard and the manufacturing of the cartons themselves are both well known and form no part of the present invention. However, in the manufacture of corrugated cartons, it is customary to determine the compression strength of the corrugated carton by edge crush testing of precision cut samples that are typically of square or rectangular dimensions. Such samples are also used for other well known types of testing. Heretofore, such samples were cut by hand, such as with a razor, knife or saw, or formed with a die.
Such prior art methods are not completely reliable since the cut, and the precision thereof, varies with the manual skill of the cutter. If the resulting cut is not square, i.e., the edges are not parallel or the cut edge itself is bevelled, it will be difficult to conduct a reliable crush test.
To obtain precision cut samples, my aforesaid co-pending '780 application, now U.S. Pat. No. 5,325,752, the disclosure of which is hereby incorporated by reference herein in its entirety, discloses a precision cutter the salient features of which are disclosed in FIG. 1 of the present drawing. Therein, the cutter 10 comprises a base plate or table 11 and a pair of cutting blades 18,20 slidably mounted to the base plate with a slide block 80 and rail system 60 for cutting movement in a direction parallel to a first guide rail 12. A pair of second guide rails 22 and 24 are spaced from each other by the predetermined distance between the pair of cutting blades 18,20 to allow the strip which has first and second cut edges simultaneously cut with the first blades to be rotated 90.degree. and positioned between the second guide rails in abutting contact therewith. Movement of the cutter blades along the cutting path completes the cutting of the strip into a precise square.
As mentioned above, the square or rectangular test panels are designed to be subjected to several different tests including an important edgewise compression test which should be performed perfectly, or precisely, parallel to the direction of the internal flutes or perfectly normal to the flute direction. To be able to produce reproducible, or duplicate, test results on similarly constructed paper board panels, it is necessary that the square or rectangular test specimen panels be uniformly and precisely cut, or formed, so that two of the test specimen panel edges are always precisely parallel to the flutes, and the other two specimen panel edges are always precisely normal to the flutes.
The hollow, internal flutes are located within the corrugated paper board panels, so that the flute direction is not always readily determined by a visual inspection of the uncut corrugated paper board panel. Nonetheless, it is possible to form a panel edge which runs approximately parallel to the flute direction, either by a trial and error process wherein the edge of the test specimen or sample is inspected after the first cut to determine the approximate extent of deviation from parallelism, or by using the heretofore described invention of FIG. 1 wherein the edge of the specimen from which a sample is being cut is first positioned against the first guide rail guide surface 12a which is precisely parallel to the cutting blades 18,20 and their direction of movement. Even with the invention of FIG. 1, however, the observer is never quite certain, from a visual inspection, whether or not the first cut is, in fact, exactly or precisely parallel to the internal flute direction. This is because the parallel cuts are being made with reference only to the extent to which the sample edge abutting the guide surface 12a is in fact precisely parallel to the internal flutes.
To obtain regular test specimens having cut edges which attempt to be precisely parallel or perpendicular to the internal flute, U.S. Pat. No. 5,146,823, issued Sep. 15, 1992 to Emerson Apparatus Company, Inc., Portland, Me., discloses a reference rod which is inserted through a selected flute in a corrugated paper board panel prior to the first cutting operation on the raw panel. The reference rod is then placed in a specific location on the cutting table surface so that opposite ends thereof project beyond the specimen edges to allow anchorage means on the table to engage these projecting ends to temporarily support the specimen on the surface with its flutes precisely oriented parallel to the path line for the cutter means. The anchoring means is disclosed as being magnets.
It is believed that numerous disadvantages inherent in the single reference rod and magnetic anchorage assembly disclosed in the '823 patent will occur that will cause the cutter system to function unreliably. For example, it is believed that the use of only a single reference rod may not maintain enough of a rigid clamping force to resist the friction and "twisting" or "torquing" affect which may occur as the cutting blade moves through the material. Consequently, it is theorized that the specimen could twist relative to the single reference rod, possibly resulting in a failure of the single rod to maintain parallelism between the flutes and the cutting blade. This problem may become even more pronounced since the frictional forces generated by a pair of cutters of the type depicted in FIG. 1 of the present specification would tend to be greater than the friction generated by the single circular cutter blade in the '823 patent.
In addition, since magnets are used in the '823 patent to anchor the opposite ends of the reference rod on the table surface, it is believed that this type of anchoring arrangement will result in crushing of the specimen at the points of anchorage and probable loss of parallelism as a result of such crushing.
It is accordingly one object of the present invention to obtain precision cut samples of corrugated cardboard to achieve reliable edge crush testing as well as other types of testing.
Another object is to provide a cutter for obtaining single or multiple precision cut samples of cut corrugated material wherein the cut edges are precisely parallel to the internal flutes in the corrugated material.
Yet a further object is to provide a method and apparatus for the precision cutting of corrugated material by initially orienting the material on a cutter support surface with reference to the fluted passages within the material and maintaining parallelism between these passages with the cutting surfaces of the cutter instrument.
Still another object is to provide a reference rod arrangement insertable respectively into plural flutes of the corrugated material to resist the frictional forces and a possible twisting or torquing effect acting on the material as the cutting surfaces advance through the material.